596827c0e9
This PR adds regression tests that catch issues where structures/classes
with class-typed fields produce HEq goals in `congr` instead of handling
Prop fields automatically.
Both tests pass on v4.28.0-rc1 (before isInstance detection changes).
## Test 1: Structure extending classes (mirrors Mathlib's GroupTopology)
```lean
structure MyGroupTopology (α : Type) extends MyTopology α, IsContinuousMul α
theorem MyGroupTopology.toMyTopology_injective {α : Type} :
Function.Injective (MyGroupTopology.toMyTopology : MyGroupTopology α → MyTopology α) := by
intro f g h
cases f
cases g
congr
```
**Failure mode:** `⊢ toIsContinuousMul✝¹ ≍ toIsContinuousMul✝`
## Test 2: Class with explicit class-typed field (mirrors Mathlib's
PseudoEMetricSpace)
```lean
class MyMetricSpace (α : Type) extends MyDist α where
dist_self : ∀ x : α, dist x x = 0
toMyUniformity : MyUniformity α -- explicit class-typed field (NOT from extends)
uniformity_dist : toMyUniformity.uniformity (fun x y => dist x y = 0)
protected theorem MyMetricSpace.ext {α : Type} {m m' : MyMetricSpace α}
(h : m.toMyDist = m'.toMyDist) (hU : m.toMyUniformity = m'.toMyUniformity) : m = m' := by
cases m
cases m'
congr 1 <;> assumption
```
**Failure mode:** `⊢ dist_self✝¹ ≍ dist_self✝` and `⊢ uniformity_dist✝¹
≍ uniformity_dist✝`
## Context
These tests are related to #12172, which changes instance parameter
detection from binder-based to `isClass?`-based. That change can affect
how structure fields are classified in congruence lemma generation.
🤖 Prepared with Claude Code
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
82 lines
3.6 KiB
Text
82 lines
3.6 KiB
Text
/-!
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# Regression tests for isInstance changes in congruence lemma generation
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These tests verify that `congr` works correctly for structures and classes
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with class-typed fields. They catch regressions from changes to how instance
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parameters are detected (e.g., using `isClass?` instead of binder info).
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Both tests pass on v4.28.0-rc1 (before the isInstance changes).
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## Test 1: Structure extending classes (mirrors Mathlib's GroupTopology)
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When a structure extends both a data class and a Prop class, the parent class
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field may be marked as `isInstance = true`. If this causes `.fixed` treatment
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in congruence lemma generation, dependent Prop fields will require HEq.
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**Failure mode:** `⊢ toIsContinuousMul✝¹ ≍ toIsContinuousMul✝`
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## Test 2: Class with explicit class-typed field (mirrors Mathlib's PseudoEMetricSpace)
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When a class has an explicit class-typed field (not from `extends`), that field
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may be marked as `isInstance = true`. If this causes `.fixed` treatment, then
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dependent Prop fields whose types mention that field will require HEq.
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**Failure mode:** `⊢ dist_self✝¹ ≍ dist_self✝` and `⊢ uniformity_dist✝¹ ≍ uniformity_dist✝`
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-/
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/-! ### Test 1: Structure extending classes -/
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-- Setup: mimic Mathlib's GroupTopology structure
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class MyTopology (α : Type) where
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isOpen : (α → Prop) → Prop
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-- A Prop-valued class that depends on MyTopology
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class IsContinuousMul (α : Type) [MyTopology α] : Prop where
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continuous_mul : True -- simplified
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-- Structure extending both a data class and a Prop class
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structure MyGroupTopology (α : Type) extends MyTopology α, IsContinuousMul α
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-- Key test: proving injectivity of the parent projection using `congr`
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-- If the toMyTopology field gets `.fixed` treatment, the Prop-valued
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-- toIsContinuousMul field will require HEq: `⊢ toIsContinuousMul✝¹ ≍ toIsContinuousMul✝`
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theorem MyGroupTopology.toMyTopology_injective {α : Type} :
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Function.Injective (MyGroupTopology.toMyTopology : MyGroupTopology α → MyTopology α) := by
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intro f g h
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cases f
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cases g
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congr
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/-! ### Test 2: Class with explicit class-typed field -/
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-- Setup: mimic Mathlib's PseudoEMetricSpace pattern
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-- A class that extends one class but has another class-typed field explicitly
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class MyDist (α : Type) where
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dist : α → α → Nat
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class MyUniformity (α : Type) where
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uniformity : (α → α → Prop) → Prop
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-- Class that extends MyDist but has an explicit MyUniformity field
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-- This mirrors PseudoEMetricSpace which extends EDist but has explicit toUniformSpace
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class MyMetricSpace (α : Type) extends MyDist α where
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dist_self : ∀ x : α, dist x x = 0
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-- Explicit class-typed field (NOT from extends)
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toMyUniformity : MyUniformity α
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-- Prop field whose type depends on toMyUniformity
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uniformity_dist : toMyUniformity.uniformity (fun x y => dist x y = 0)
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-- Key test: extensionality theorem using `congr`
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-- If toMyUniformity gets `.fixed` treatment (because it's class-typed but not
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-- a subobject field), then `congr` will produce HEq goals for dependent fields
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protected theorem MyMetricSpace.ext {α : Type} {m m' : MyMetricSpace α}
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(h : m.toMyDist = m'.toMyDist) (hU : m.toMyUniformity = m'.toMyUniformity) : m = m' := by
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cases m
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cases m'
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-- After cases, we need to prove the constructors are equal
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-- `congr` should produce goals for data fields (dist, toMyUniformity)
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-- and automatically handle Prop fields (dist_self, uniformity_dist) via casting
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-- If toMyUniformity gets `.fixed` treatment, we'd see HEq goals like:
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-- `⊢ dist_self✝¹ ≍ dist_self✝` or `⊢ uniformity_dist✝¹ ≍ uniformity_dist✝`
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congr 1 <;> assumption
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